Pressure responsive control device



July 1952 F. c. DOUGHMAN 23,516

PRESSURE RESFONSIVE CONTROL. DEVICE FOR VACUUM GLEAN ERS Original FiledJune 12, 1946 4 Sheets-Sheet 1' INVENTOR. FHMAN c. nor/mum w /a 'AFW y1952 F. c. DOUGHMAN Re. 23,516

PRESSURE RESPONSIVE CONTROL DEVICE FOR VACUUM CLEANERS Original FiledJune 12, 1946 v 4 Sheets-Sheet 2 g\ Q Q N 1/, I T T INVENTOR.

FERMAN anal/ 1mm BY y 1952 F. c. DOUGHMAN Re. 23,516

PRESSURE RESPONSIVE CONTROL DEVICE FOR VACUUM CLEANERS 4 Sheets-Sheet 3Original Filed June 12, 1946 TIME DELAY SWITCH INVENTOR. FERMAN C.DOUGHMAN July 1, 1952 F. c. DOUGHMAN PRESSURE RESPONSIVE CONTROL DEVICEFOR VACUUM CLEANERS Original Filed June 12, 1946 4 Sheets-Sheet 4 A BOTHSWITCHES CLOSED v y W BOTH SWITCHES OPE I5 20 SUCTION ON SYLPHON4IINGHES OF H O INVENTORQ FERMAN c. DOUGHMAN BY i9! TORNEX Reissued July1, 1952 PRESSURE RESPONSIVE CONTROL DEVICE FOR VACUUM CLEANERS Ferman C.Doughman, Darien, Conn., assignor to Electrolux Corporation, OldGreenwich, Conn., a corporation of-Delaware Original No. 2,580,643,dated January '1, 1952, Se-

rial No. 676,318, June 12, 1946. Application for reissue March 25, 1952,Serial No. 278,366

Matter enclosed in heavy brackets II appears in the original patent butforms no part of this reissue specification; z'mattcr printed in italicsindicates the additions made by reissue.

22 Claims.

This invention relates to control'devicesand is particularly concernedwith control devices which are responsive to pressure or suctioncharacteristics of a fluid flow-system. One practical application of theinvention is for use in suction cleaners to control certaininstrumentalities thereof in response-to variations in the operatingcharacteristics of the device.

More specifically one preferred application of the broad inventiveconcept is for the electrical control of certain. suction cleanerfunctions in response to a decrease-in cleaning eificiency due to adecrease ofair flow at the suction nozzle, such decrease of air flowbeing responsive among other things to the amount of accumulated dirt inthe dust separating and receiving element. Thus the device functions inresponse to a requirement for the cleaning or exchanging of the dustseparating element.

Throughout the following specification the operatingcharacteristicsare.discussed in terms of suction measured in inches ofWater which such suction will displace in a. manometer. Air flow isreferred to in terms of cubic feet per minute. The flow of air through acleaning nozzle is caused by certain suction characteristics at variouspoints in the system. Otherwise stated,

pressure differences are caused to exist whereby air flow is induced,howeven'since such pressure differences are manifest as air flow and.assuction, it is believed that a clearer and more accurate understandingof the invention may be had by reference to suchmanifestation ratherthan to the absolute pressure. Theterm vacuum is sometimes loosely andeven inaccurately applied in the present art andfor that reason isherein avoided, but it will be understood that where suction and airflow are here discussed they may be interpretedin terms of absolutepressures, pressure differences or the application of vacuum. Obviouslyno such arbitrary choice. of language may be resorted to as a means fordistinguishing the present inventive concept from similar developmentsin the art to which this invention relates.

While the present disclosure uses the conventional expression "suctioncleaner as generic term for the device to which the inventive concept ishere appliedyit will be understood that the invention is broadlyapplicable to pressure systems or flow devices other'than suctioncleaners. For the purpose of this disclosure the term suction cleanerrefers to domestic cleaning devices in which suction induces'airflow'from the surface to be cleaned through ardustseparatingandretaining member usually-a porous bag through which clean airpasses-leaving. dust and dirt entrained by the air flow within the bag.Obviously the inventiveconcept is applicable to other types of suctioncleaners as for instance, those wherein non-removable dust separatingmeans are employed. The specific embodiment discloses the inventionapplied to a cleaner in which-the bag is mountedbetween thecleaningnozzle anda motor-fan unit, but itwill be understood that it may beequally well applied to cleaners in which the bag is applied to theexhaust of the fan as with so-called bag-on-handle cleaners.

As is readily understood by those skilled in the art, the cleaningefficiency of suction cleaners is directly responsiveto the velocityof-air flow at the surface bein cleaned. Such velocity is responsive tothe restrictive affects of the free area permitting air flow at thesurface being cleaned, the restrictive characteristics of the suctionhose or passage between the nozzle and the cleaner body, and therestrictive affect of the dust separator as well as the primary suctioninduced by the motor-fan unit of the device. While the restrictiveaffect of the hose is a separate element of the total restrictions ofthe system and varies with rate of flow, it adds to the nozzle and coverorifice restrictions to form a total before the bag restriction andconsequent pressure drop. Thus in the following consideration thesetotal restrictions are spoken of in terms of nozzle restriction alonesince-witheach nozzle the hose and cover are a necessary additiverestriction. Assuming that the primary suction induced by the fan isdirectly responsive to-theaccumulated sum of these flow restrictions,ignoring for the sake of clarity, the possible change under load ofcertain-types ofmotors-which may be used, then the air how for anygivennozzle restriction will be directly responsiveto the amount of suctioninduced by the fan and the amount of restriction to flow imposed by thecharacteristics of the dust separator.

The amount of air flow for a given nozzle restriction may thus bedetermined by a measurement of the primary suctionat the fan and ameasurement of the suction inwardly of the nozzle. Sincetherestrictiveness of the hose or passage from nozzle to separator isafactor of air flow through the-nozz1e,- this latter suction may in thestructure herein depicted be taken by a reading directly in front of thedust separator. Such readings will, of course; give a direct measure ofthe restrictive afiect of the dust separator.

vIt will, of course, be recognizedjthat duringcleaning accumulateddirtin the dustbag tends to fill the interstices of the bag, thusreducing free flow of clean air therethrough. Such resistance worksagainst the eiiorts of the motor-fan unit to maintain air flow throughthe cleaning nozzle and a point is reached at which time the cleaningefficiency is so'reduced that the emptying or changing the dust bag isrequired. I

Since the adequate air flow is a factor of the nozzle resistance as wellas dust separator resistance, it will be seen that mere bag resistanceis not a reliable guide for determining the operating efliciency of thedevice. Thus neither the weight nor volume or accumulated dirt nor thepressure drop through the bag should be relied on to operate a controlsystem. Furthermore,

since both the suction before the fan and the suction before the dustseparator vary for diiierent rates of air flow even though such ratesmay be adequate for the type of nozzle being employed a proper controlsystem cannot rely on either one or the other of such suctions alone.

From the foregoing, it will be seen that a control system, which isjointly responsive to the suction at the inlet of the fan and to thesuction In cleaners currently in use, it is frequently difiicult orimpossible for the operator to properly gauge the point at which thecontinuously decreasing efiiciency renders her efforts upprofitable.Attempts have been made to design control systems for gauges andindicators which will produce visual or audible signals to call theoperators attention to'the fact that the bag should be emptied orchanged and in certain types of cleaners, designed to automatically openand eject, or present for removal, the dust bag when it is full, controldevices are desired which are responsive to the decreasing of efiiciencyabove referred to. The present invention is herein disclosed asfulfilling this requirement.

The present invention is directed to a control means responsive tosuction measured at spaced points in a flow system and may be generallydefined as comprising a pair of suction responsive elements; one ofwhich is arranged to respond to the suction which produces inflow of airfrom the cleaning nozzle, while the other is arranged to respond to thesuction which produces outflow of air from the bag. Both of thesedevices cooperate to control some associated instrumentality in responseto predetermined variations in such pressures.

It is among the primary objects of the invention to provide a controldevice which will be responsive to a given relationship of suctionswithin a fluid flow system.

A further object of the invention is to provide 4 a control system whichwill not be affected by variations in fluid flow: caused by' extraneousforces acting beyond the points of application of the control system.

Numerous other objects and features of the present invention will beunderstood from a consideration of the following specification taken inconjunction with the accompanying drawings, in which;

Fig. 1 illustrates the system as applied to one type of vacuum cleaner;

Fig. 2 is a view similar to Fig. 1 showing the relation of cleaner partsafter actuation of the control device;

Fig. 3 is a diagrammatic illustration showing a circuit which may beused in connection with the present control system;

Fig. 4 is a view similar to Fig. 3 of a modification of the diagram ofFig. 3, and

Fig. 5 is a graphical representation of the operation of the inventionunder various operating characteristics.

In the present embodiment of the invention, the suction responsivedevice comprises a pair of Sylphon bellows, each of which controls amicroswitch. The microswitches are placed in series in a controlcircuit, the arrangement being such that the control circuit isenergized only when both of the microswitches are closed in response totheir actuation by the Sylphon bellows. the present disclosure, theinventive concept is applied to a suction cleaner, wherein one of theSylphons is in communication with the air passage leading from thecleaning nozzle, while the other is arranged to be in communication withthe suction utilized to induce flow through the dust bag. Thearrangement is such that when the suction in front of the bag fallsbetween a predetermined point thus diminishing the air flow at thenozzle, the first Sylphon will close its microswitch, while the secondmicroswitch will be closed when a predetermined suction pressure isestablished in front of the fan. When the motorfan unit is runningsuction will be induced such as to cause the second microswitch to beclosed and therefore, if adequate fiow is prevented through the nozzle,it will be registered by decreasing suction in the passage from nozzleto bag and the first microswitch will close, thus completingenergization of the-control circuit.

While the presentation of the invention discloses its application to atank type cleaner which is arranged to be opened in response to decreasein efficiency and the control circuit is arranged to actuate the openingmechanism, it will be understood that the circuit may have various otherapplications, both in and out of the suction cleaner field. The circuitmay, of course actuate a signal device instead of the opening mechanismor may be arranged to operate a signal device and/or to control themotor as well as actuating the opening device.

Referring more particularly to the drawings, the present invention isdisclosed as applied to a novel tank type vacuum cleaner, the structureof which is disclosed in detail in the 'copending application of GustafEinar Lofgren filed July 2, 1946, Serial No. 681,074 (now U. S. Patent2,534,280 dated December 19, 1950). In view of the detailed disclosureof the above-identified application to which reference may be had, itwill sufiice to describe the cleaner as a floor supported tank typecleaner having a body Ill within which is mounted a motor-fan unit I ladapted to draw air in through the body inlet [2, and discharge the samethrough the body outlet |3. Slei ghs |4 support the structure inslightly spaced relation from the floor and a handle I5 is provided forcarrying the device. Mounted at one end ofthe handle there is a switchbutton IE to provide manual control of the motor unit I l, thearrangement being such that the button may be conveniently actuated bythe foot of the operator. As will be hereinafter described, meansresponsive to the control system may also actuate the switch I6.

Forwardly of the body In a housing I! extends, between the walls ofwhich is pivotally mounted a chamber l8 which encloses a dustreceptacle. The rear end of the chamber I8 is provided with an airoutlet of such configuration as to sealingly engage the inlet l2 whenthe casing is in horizontal position as shown in Fig. 1. The chamber I8is biased to the tilted position shown in Fig. 2 by spring 2|. The frontof the chamber is normally closed by front cover 22 pivoted as at 23 tothe housing IT. A latch 24 pivoted as at 25 upon the chamber 8 isprovided to perform the dual function of securing the cover 22 closedand securing the chamber l8 in its horizontal and operative position.Latch 24 is connected for operation by a solenoid 26, mounted upon thechamber l8, which engages the latch 24 so that upon energization of thesolenoid, the latch will pivot clockwise to release the cover,permitting the spring 2| to tilt the casing to the position shown inFig. 2, thus presenting the dust bag for ready removal from the chamber.

If desired, ejecting means may be employed, as disclosed in thecopending application above referred to, for ejecting the dustreceptacle when the housing is tilted.

The front cover 22 is preferabl provided with 'a hose receiving coupling21, a hose 28 being removably secured therein and being adapted toreceive suitable cleaning tools as commonly used in connection with tanktype cleaners. As shownv in Fig. l the hose while capable of directattachment to. a cleaning tool may lead to a tubular handle or wand W towhich a floor orrug cleaning nozzle N is attached. The coupling 21 ispivotally mounted on the cover by hinge 29 and is normally secured inclosed position by a spring latch 33, the arrangement being such thatwhen the cover i open'the coupling may move pivotally to permit covermovement without undue disturbance of the hose position. The cover isalso provided with an inlet tube 3|, the mouth 32 of which extendsthrough end 33 of the dust receptacle I!) when the cover is closed andthe device is in the operating position shown in Fig. 1.

The present structure is designed to use any one of various types ofdust receptacles which are characterized by porous bodies usually havingrigid covers, centrally apertured to receive the mouth 32 of the tube3|. These receptacles are preferabl formed of paper, the centralaperture of the cover being provided with a sealing device preferablyarranged to seal against the mouth 32 and upon withdrawal of the tube,to close the bag to provide a sealed and disposable dust receptacle.

The control device of the present invention comprises a pair of Sylphonbellows and 4| with which are associated microswitches 42 and 43. Tubes44 and 45 communicate with the interior of the bellows 40 and 4|,respectively. Externally the bellows are open to the atmosphere, thearrangement being such th-atvariationsin suctioncommunicatedto theSylphons through the tubes will cause a responsive contraction orelongation thereof by. which the microswitches will be actuated.

In the application of-th'e-present invention to the structure hereinshown, the forward or inlet Sylphon 4B is connected by its tube 44 withthe tube 3| whereby the Sylphon will be responsive to the suction withinthe. tube 3| and thus to flow of air through the nozzle N with which itcommunicates through the hose 28. The rear or fan suction Sylphon 4| isconnected by its tube 45 to the inside of the chamber I8 and thus isresponsiveto the suction within the casing, which suction is the primarymotor-fan suction.

It will be understood that with a new or clean bag in the chamber l8 andwith the housing closed as in Fig. 1 and the motor-fan unit operatingthe suction inside of chamber l8 will be. communicated with minimumresistance to the inside of the bag I!) since air may readily flowthrough the pores of the bag. Similarly since the hose itself i designedtoprovide minimum resistance of air flow, a comparative suction will beobtained within the nozzle N. Such suction induces rapid inflow of airacross the surface to be cleaned, thus entraining dust and dirt which iscarried to the bag l9 and strained by the pores thereof, clean air beingpassed through to be discharged to the atmosphere.

The invention includes a control circuit including the microswitches 42,43, solenoid 26 and a switch operating coil 45 (not visible in Figs. 1and 2). While various circuit arrangements may be advantageouslyemployed depending upon the specific application of the broad inventiveconcept the present invention embraces a circuit of the type shown inFig. 3, such circuit having particular advantages in the application ofthe invention to the specific cleaner structure of Figs. 1 and 2. InFig. 3 the power supply line is represented by conductors 50 and 5|. Theconductor 50 leads through switch |6'to the motor H, the return circuitbeing completed through conductor 5|. The control circuit throughmicroswitches 42, 43 and coils 26 and 45 comprises conductor 52 leadingfrom conductor 50 at a point intermediate switch IB and motor II. Fromsuch intermediate point between switch It and motor conductor 52 extendsto microswitch 42 and thence by conductor 53 to microswitch 43, thusplacing the microswitches in series. From microswitch 43 the controlcircuit extends through conductor 54 to coil 26 and thence by conductor55 to coil 45, thus placing the coils in series with each other and inseries with the microswitches 42 and 43. From coil 45 conductor 56completes the control circuit by leading to conductor 5| constitutingthe other side of the line.

With the above circuit arrangement it will be seen that with switch l6open and no power flowing to the motor no energization will be providedfor the control circuit. With switch Hi closed, the control circuit willbe energized to the micro-switches and since the switches are in series,both must be closed in order to complete the circuit through the coils2B and 45. With either one of the microswitches open, the controlcircuit is de-energized.

It will be noted that in the above arrangement, the action of Sylphon 40and switch 42 is the reverse of that of Sylphon 4| and switch Sylphon4|] is set to bias switch 42 to closed position when no suction isapplied and the Sylphon 48 moves switch 42 to open position in responseto the application of predetermined; suc- 7 tion; conversely Sylphon 4|biases switch 43 to open position when no suction is applied and. closesthe switch in response to the application of predetermined suction.

In the present device with switch l6 open and the motor H de-energized,microswitch 42 is closed While microswitch 43 is open as shown in Fig.3, the Sylphons 40 and 42 biasing the switches to these positions whenno suction is applied. As will be more fullv explained hereinafter, whenswitch It is closed and the motor I I energized, the normal operatingconditions of the cleaner will provide suction in Sylphon 40 causingswitch 42 to open, while at the same time applying suction to Sylphon 4|closing or tending to close switch 43 and the control circuit will notbe energized. When, during the operation of motor ll, suction applied toSylphon 4!] falls below a predetermined amount while suction applied toSylphon 4| is such as to close or continue to retain switch 43 closed,the control circuit will be established, thus energizing coils 26 and45. The energization of coil 26 releases latch 24 permitting cover 32 toopen and chamber 3 to tilt upwardly. The energization of coil 45 willdraw downwardly rod 51 connected with switch I6, the arrangement beingsuch that downward movement of the rod 51 opens switch It, thusde-energizing motor II as well as the control circuit. Similarly, if thesuction maintained on Sylphon 40 is not sufiicient to hold switch 4|open, while suction applied to 4| is less than the predetermined settingthereof, switch 43 will remain open and the control circuit will not beenergized until the suction on Sylphon 4| increases sufficiently toclose switch 43.

An important and advantageous feature of this circuit of the inventionis the fact that the switch I6 dominates the control circuit includingthe microswitches 42 and 43. Upon energization of the control circuit,switch I6 is opened by coil 45 to thus interrupt the supply of currentto the contro1 circuit, and hence the microswitches 42 and 43 are neverrequired to break the circuit while the latter is energized, but only tomake it. During the operation of the device, while switches 42 and 43may frequently open and close, they do so without transmitting currentexcept when both are closed at the same time, whereupon the switch It isopened by coil 45. This arrangement provides a long useful life for theswitches, since it is the arcing of switches upon breaking the circuitwhich contributes most to their wear and deterioration.

Fig. 4 of the drawings illustrates a modification of the circuit of Fig.3 and provides a time delay device which in some instances may bedesirable. As in Fig. 3 power is supplied to the circuit from a suitableoutside source through conductors 5D and 5|. The switch |6 is insertedin conductor 50 leading to one side of the motor while the other side ofthe motor H is connected by conductor 5| to the other side of the line.The conductor 50 is also connected by a conductor 5'2 to microswitches42 and 43 which are arranged in series and therefrom lead to the timedelay switch indicated by the numeral 58. The return circuit from thetime delay switch to the conductor 5| is indicated by the numeral 56.Unlike Fig. 3 in this circuit, conductor 52 is connected ahead of switchHi. This arrangement is such that when Sylphons 40 and 4| close both themicroswitches 42 and 43, circuit is established to the time delayswitch. Associated with the time delay switch is the solenoid 26 whichoperates the latch 24 and in series therewith a coil 45 which uponenergization moves rod 51 connected with switch Hi. When both switches42 and 43 close and the circuit is first established through themicroswitches and the time delay switch, no circuit is at firstestablished through the coils 26 and 45. However, after a predeterminedpassage of time, suitable means within the time delay switch such as athermally responsive element acts to include the coils 26 and 45 in thecircuit, thus energizing them to actuate the latch 24, opening the coverof the cleaner and at the same time energizing coil 45 which moves rod51 to open the switch I6, thus breaking the circuit to the motor II. Itwill be seen that with the cover open and the housing tilted theSylphons will return to their normal or nonoperative position with thecontrol circuit broken by one of the microswitches. The purpose of thetime delay device in the present circuit is to prevent pressure surgesor other purely temporary dislocations of the .suction relationshipsfrom actuating the controller.

Referring now to Fig. 5, characteristics of suction conditions and airflow during the operation of the cleaner are graphically set forth. Itwill be understood that this figure presents a generalization ofoperating characteristics based upon the operation of one type ofcleaner now on the market. Specific models of such cleaners may operatein a manner varying somewhat from the present graphical presentation andother types of cleaners may have operating characteristics more widelydeparting from the present presentation. However, the basic operatingcharacteristics of all suction cleaners are therein depicted, althoughthe quantitative data set forth may not always be in accord with thegraph. In the graph the ordinate represents suction as applied to theSylphon 40 and is calibrated upwardly from the abscissa in inches ofWater displaced in a manometer. The total suction here calibrated isforty-five inches. It will be understood, however, that difierentcleaners may have different total suction throughout the system and soan accurate graph therefor, would vary accordingly.

The abscissa of the graph represents suction at the motor head which isapplied to the Sylphon 4| and is likewise calibrated in inches of wateras measured by a manometer and depicts a maximum suction of forty-fiveinches in keeping with the maximum suction represented by the ordinate.Rate of air flow is represented on an hypotenuse and is calibrated incubic feet of air flow per minute, the maximum flow for the suctions setforth being ninety cubic feet per minute. It will be observed that theair flow increases downwardly with respect to the ordinate and decreasesas the suction depicted by the abscissa increases, thus there is zeroair flow when maximum suction is reached by both Sylphons which would bethe case in a sealed circuit with the motor in operation. Similarly amaximum air flow of ninety cubic feet per minute is depicted when thesuction on both Sylphons 40 and 4| is zero. Obviously, with no suctionthere would be no air flow at all, but with decreasing resistance toflow, the volume per minute increases while the suction required toproduce it decreases, and consequently the theoretical point of zerosuction is approached, and the graph thus accurately depicts thefundamental operating characteristics.

In the graphical presentation of Fig. 5, the

point of five inches of suction has been arbitrarily chosen as the pointat. which the microswitch 42 associated with Sylphon 40 is closed, theswitch being open when the 'suctionapplied to the Sylphon '40 is greater.than five inches of water, while the switchis closed when five or lessinches of suction is applied to the Sylphon 40. vWith respect totheSylphon 4|, a point of twenty-five inches of suction has beenarbitrarily selected as a point for operation of the microswitch 43associated therewith, the switch being open when a suction of less thantwenty-five inches of water is applied to the Sylphon 4| and beingclosed when greater, suction is applied.

In the graph, the shading inclined upwardly to the right indicates thefield in which Sylphon 4| has caused the switch 43 to close, while theshading inclined upwardly to the left depicts the area in which theSylphon 40 has caused the switch 42 to be closed and thus the doubleshaded area depicts a field in which both switches are closed.

As indicated by the downwardly directed vertical arrows associated withthe air flowline, it will be understood that the rate of air fiow for .agiven point in the graphis to be read by projecting upwardly such pointin a vertical line until it intersects the air flow line, thus at theupper left-hand corner of the double shaded area Where fiveinchsuctionon the Sylphon 49 is. maintained, while twenty-five inches ofsuction is maintained on the Sylphon 4|, the flow of air will be fortycubic feet per. minute. Again it is pointed out that these values areentirely approximate and may differ as between various cleaners of thesame model and between various types of cleaners.

In Fig. 5 lines A, B, C and D have been drawn extending from spacedpoints on the air flow lines toward the junction .of theordinate and theabscissa where suction at the Sylphon 40 is zero and suction on theSylphon' 4| is maximum. Inthe operation of the cleaner, it will beunderstood that as resistance to flow increases through the filter bag,the difference between suction registered by the Sylphon 40 and thatregistered by the Sylphon 4| will increase and so for any givenrestriction of the nozzle. and hose a line depicting the flowcharacteristic with such restriction will move downwardly and to theright of the graph as the resistance to flow by the bag increases,hence, the general radiating characteristic of the lines with respect tothe juncture of the ordinate and abscissa. The uppermost of these lines,line A, which leads from a point of twenty cubic feet er minute of airflow which corresponds ap- P proximatelywith thirty-five inches ofsuction on Sylphon 40 and thirty-five inches on Sylphon 4| represents atits upper end a theoretical condition in which there is no pressure dropthrough the bag, but in which there is considerable flow resistanceahead of the bag and Sylphon 40, as

would be caused bya very restricted cleaning nozzle.

The line moves rapidly downward and more gradually to theright showingthat as the bag increases its resistance due to the accumulationofdirt,the suction at Sylphon 4|) will rapidly decrease, while the suctionapplied by the fan .to Sylphon 4| willgradually increase for this 10will be closed. At such point, rate of air flow as determinedbyprojecting upwardly the point of intersection of line A with theabscissa for five inches of suction on-Sylphon 40 will be seen to besomething less than ten cubic feet per minute.

The line A is a characteristic representation of operating conditionswhen the nozzle exerts an extremely high restriction to air flow as whena rug cleaning nozzle is being held tightly against the nap of a rugbeing cleaned. The point of intersection of line A'with the'air flowline, represents the air flow with such a, nozzle with atheoretically"perfectly clean: bag which offer no flow resistance-andhencej'the suction applied to Sylp-hons 4D and 4| are equal. Since nobag will actually have zero resistance, the intersection of lines A, B,C, and D with the air flow line is theoretical, but the line is accuratein depicting a decrease in Sylphon 4D suction and increase in Sylphon 4|suction as the bag] resistance due to accumulated dirt increases.

An important characteristic of the present system which should be noted,is that with the highly restrictive nozzle orifice depicted by line A,total volume of air flow is quite small as compared with the air flowdepicted by lines B, C and D. However, such high restriction may be theresult of either a very small cleaning tool as used for upholsterycleaning or' as aresult of pressing the nozzle opening close against thesurface being cleaned, in any event the total crosssection of airpassage at the nozzle is quite. small and hence, while volume ofairiflowis small, velocity of air flow is quite high and since air flowvelocity at thenozzleis; th main measure of cleaning efficiency,successful cleaning1may be carried on with such a-nozzle even though theair now volume per. minuteis less thanpractical for less restrictivenozzles. Thus, the line'A enters the double shaded controloperatingifield at a point where relative suctions are more divergentand air flow. much less than depicted by lines B, C and D.

Referring now to line D of .Fig. 5, this line extends from a. point ofair flow of eighty cubic feet per minute on the air flowline towards thepoint of juncture of the ordinate and abscissa and represents thesituation in which very little resistance to air fiow by either thenozzleor the hose is present, or for instance, when the hose is removedfrom the cleaner. In this condition since the Sylphon 4|] is arrangedclose to the hose coupling, it is subjected to substantial atmosphericpressure and the suction applied there-to will be below the abscissa offive inches for. Sylphon 40suction and thus with the machine operatingunder such conditions the line D will be at all times within the shadedarea which represents that the switch 42 is closed. Under theseconditions as the bag gradually increases'its resistance, the suction onSylphon40 will further diminish slowly,' while the suction applied toSylphon 4| will-rapidly increase with a conse quent decrease in airflow. At a point of air flow of forty cubic feet per minute, the line Dintersects the ordinate twenty-five at which point switch 43 will closeto actuate the control circuit. It will be understood, of course, thatwith the hose removed from the cleaner, very little dirt will enter andthe bag condition will change very slowly. However, since it is notdesirable to have the control circuit actuated merely by a temporaryremoval of the hose when the bag is substantially clean, the:pointtwenty-five has been elected for actuation of switch43. It will 11 s benoted that although the volume of air flow is high at this point, thevelocity is quite low since there is a maximum opening for the air flow.

Another advantageous characteristic of the present system is that, whileit is possible to completely fill the bag with loose fibrous materialsuch as rug nap, without causing a sufficient clogging of the bag toenergize the control circuit, nevertheless, the circuit will beenergized not by virtue of pressure drop through the ba but as aresultof. clogging tube 3| and/or filling tube 44 blocking suction toSylphon 4|),thus closing switch 42.

Lines B and C represent flow characteristics when nozzles ofintermediate restrictiveness are applied to the hose. Line B forinstance, may be taken as representing flow characteristics when the rugcleaning nozzle referred to in connection with line A is raised somewhatfrom close contact with the surface being cleaned, in which case theavailable orifice for air flow at the nozzle is increased. However, withsuch increase, air velocity at the nozzle decreases. As the line Bapproaches the abscissa live, it will intersect it to enter the doubleshaded area and energize the control circuit at a point of considerablymore than ten cubic feet per minute of air flow, but despite suchincrease in air flow since the nozzle opening is greater, the velocityis substantially the same. Thus, the cleaning efliciency at this pointwill be approximately the same as the cleaning eficiency at the pointwhere line A intersects the abscissa five and thus, while the controlcircuit is responsive to increase in resistance due to the accumulationof dirt by the bag, it also is so arranged as to respond when cleaningeficiency, due to velocity decrease at the nozzle, falls below apredetermined point.

Similarly, line C represents the air flow when nozzle resistance isfurther decreased as in the use of floor brushes. In this case air flowis high, but since resistance is low the cleaner will operate for sometime before the line C enters either of the shaded areas. At a pointrepre senting forty cubic feet per minute flow, the lint C enters theupper shaded area, at which point the microswitch 43 will be closed,however, due to the condition of the bag, suction applied to the Sylphon40 will be maintained well above the ordinate five. As the bagresistance increases, suction on Sylphon 40 decreases and suction onSylphon 4| increases. Ata point depicting approximately twenty cubicfeet of air flow per minute, the line C intersects the ordinate five andswitch 42 closes and the control circuit is established. Again it willbe noted that with a large orifice, the volume of'air flow must be highto establish the requisite velocity of air at the nozzle-and so thecontrol circuit is established at a point representing less resistanceby the bag, but at a point substantially uniform with respect tocleaning efficiency at the nozzle.

Again it is pointed out that Fig. 5 represents a schematic and graphicpresentation of fundamental operating characteristics and it is notintended as an accurate quantitative analysis of any particular suctioncleaner. Consideration of Fig. 5, however, will indicate that thepresent system is one in which the control circuit is ese tablished inresponse to a substantially uniform degreeof cleaning efficiency andprovides in ad-- dition thereto, a means for precluding actuation of thecontrol when the hose is temporarily removed, but while the bagresistance is still low enough to permit efficient cleaning whensuitable cleaning tools are applied. Obviously the lines A, B, C and Dare merely suggestive of the characteristics of flow and suction undervarious conditions and are not intended to represent any particular typeof nozzle or cleaning tool.

In further consideration of Fig. 5, it will be understood that the airflow and suction there depicted,corresponds to the normal operation ofthe cleaner and represents substantially ideal conditions. In actualoperation, however, fluctuations will occur as, for instance, when a rugcleaning nozzle suddenly passes over the edge of a rugor when the/nozzleis lifted andFig. 5 has not been complicated by an attempt to depictsuch transient changes. One example of such conditions is, when thesuction opening is completely blocked as by flat contact of the nozzlewith a solid surface or when the hand is placed against the nozzle orhose. Such happenings produce surges, back pressures and swirlingphenomena, which are usually temporary in nature and do not usuallydisturb the effectiveness of the present control. However, withreference to Fig. '4, it will be noted that in an apparatus in whichsuch sudden pressure changes are so extreme as to inadvertently energizethe control circuit, the time delay switch 58 may be inserted and thusalthough both switches 42 and 43 may be temporarily closed, they willnot actuate the control until the condition becomes static, which wouldnot have been the case had the switches responded to surges or the like.

It will be seen that while the present control system is responsive topressure drop through the bag and hence to the amount of weight ofaccumulated dirt therein, the system is likewise responsive to air flowand to suction applied to the bag. Control systems for the actuation ofsignals and indicators have heretofore been proposed responsive to suchconditions. In no former system, however, has the .control beenresponsive to combined suction relationships, nor

has it been responsive to cleaning efiiciency as determined by nozzleflow velocity. In the present system, while the'Sylphon 40 appears inmost instances to be the primary controlling factor, the Sylphon 4| actsto prevent operation of the control when with a clean bag the hose isremoved or when with a clean bag voltage drop occurs which reduces thetotal pressure drop through thesystem In theoperation of the device withthe parts as indicated in Fig. 1 and with the motor not energized, theSylphon 40 associated with the inlet tube of the cleaner retains themicroswitch 42 closed, while the'Sylphon 4| associated with the housingI 8 retains the microswitch 43 open, these being the normal inoperativesetting for the microswitches. In such inoperative condition it will beunderstood the switch I5 has been so actuated as to break the circuit tothe motor ll. When the device is to be used, the switch It is actuatedto close the circuit to the motor whereupon the fan is operated as asuction device, thus establishing a suction in the chamber l8. Witha'clean bag the action of the fan will thus cause a substantiallysimilar suction in the tube 3|, hose 28, wand W; and nozzle N, therebycausing'a rapid inflow of air through the nozzle. Such suction in thechamber |8 causes an actuation of the. Sylphon 4| which will close themicroswitch 43 which would otherwise establish the controlcirjcuit.However, since the reduction in pressure in the housing I8 issubstantially the of such devices.

its inoperative closed position. If such increase in pressure takesplace while the fan is operating and-while suction is thus applied tothe bag IS, the control circuit-will be completed since under suchcircumstances 1 the sylphon i 41 isretaining the microswitch 43 clos'ed.-"=In other words, in response to predetermined pressure dropthrough'the bag, or rate of air fiow, as represented by a predeterminedamount of suction difference between the suction of thetube 3l and thechamber l8,-'the circuit will be established.

-When-such pressure drop is a result of accumulated dirt in the bag 19,the pressure drop will be maintained and the microswitches will'the-n beclosed, thus actuating the latch 24 to open the cover andsimultaneously'therewith energizing coil 51 to open the switch [6 thusde-enereizing the motor H. The cleaner will then be in the positionshown in Fig. 2 with the bag [9 presented for disposal. After the bag isemptied or replaced by a clean bag, the housing 18 is lowered to thehorizontal position shown in Fig. l and the cover is closed whereuponthe latch 24 acts to retain the cover closed and the housing inoperative position. The device is then ready for another cycle ofoperation.

from the foregoing, it will be seen that the present invention providesan eifective control system accurately responsive to suction differencesin a fiuid'fiow system and one which is particularly adapted for use invacuum cleaners as a means responsive to the cleaning efficienciesObViOLISIy the invention is not limited to the specific embodiment orapplication here illustrated. Numerous changes in design, application,and the full use of equivalents may be resorted to without departurefrom the spirit or scope of the invention as outlined in the appendedclaims.

What I claim is:

1. In a vacuum cleaner, a housing, a dust sepa rating member in saidhousing, means for producing flow of air through said member, a firstair pressure responsive device operable in response to an increase inpressure ahead of said member, a second air pressure responsive deviceoperable in response to a decreasein pressure behind said member to avalue less than the pressure at which said first device is operable, andmeans actuated in response to concurrent operation of said devices.

2. In' a vacuum cleaner, a housing having an inlet opening, means forproducing flow of air into said housing through said inlet, a dustseparating-member in said housing in the path of air flow between saidinlet and said means, a first air pressure responsive device operable inresponse to an increase in pressure ahead of said member, a second airpressure responsive device operable in response to a decrease inpressure between said member and said means, to a value less than thepressure at which said first device is' operable, and means actuated inresponse to concurrent operation of said devices.

3. In a vacuum cleaner, a housing. having an inlet opening, means forproducing flow of air into said housing through said inlet, a dustseparating member in' said housing in the path of air fiow between saidinlet in said means, a first element movable in response to variationsin air pressure ahead of said member, a first electric switch operableby movement of said element resulting from an increase in pressure, asecond element movable in response to variations in air pressure betweensaid member and said means, a second electric switch operable bymovement of said second element resulting from a decrease in pressure toa value less than that effective to operate said first switch,an'electric circuit including both of said switches, and means in'saidcircuit'actuated by concurrent operation of said switches.

4. In a-vacuum cleaner, a housing having an inlet opening, means forproducing flow of air into said housing through said inlet, a dustseparating member in said housing in the path of air'fiow 'between saidinlet in said means, a

first element movable in response to variations in air pressure aheadofsaid member, a first electric switch closablej-by movement of said firstelement resulting from an increase in pressure, a second element movablein response to variations in air pressure between said member and saidmeans, a second electric switch closable by movement of said-secondelement resulting from adecrease in pressure to a value less than thateffective to close said'firstswitch, and electric circuit including bothof said switches'in series,

and means in said circuit actuated by concurrent closing-of saidswitches.

5. In a vacuum cleaner, a housing forming a dust separating chamberhaving an air inlet opening, means for producing fiowof air into saidchamber through said inlet, a dust separating member in said chamber inthe path of air fiow between said inlet and saidmeans, a first airpressure responsive device operable in response to an increase inpressure in said inlet opening, a second air pressure responsive deviceoperable in response to a decrease in pressure between said member andsaid means, to a value less than the pressure at which said first deviceis operable, and means actuated in response to concurrent operation ofsaid devices.

'6. In a vacuum cleaner, a housing forming a dust separating chamberhaving an air inlet opening, means for producing flow of air into saidchamber through said inlet, a dust separating member in said chamber inthe path of air flow between said inlet and said means, a first of saidswitches.

7. In a vacuum cleaner, a housing having an inlet opening, means forproducing flow of air into said housing through said. inlet, a dustseparating' nember'in said housing in the path of air .flow'between saidinlet in said means, a first bellowshaving its interior communicatingwith said path of air flow ahead of said member and its exterior subjectto atmospheric pressure, a first switch operable in response toexpansion of said bellows resulting from an increase in the pressureahead of said member, a second bellows having its interior communicatingwith said path of air fiow between said member and said means and itsexterior subject to atmospheric pressure, a second switch operable inresponse to contraction of said second bellows resulting from a decreasein the pressure between said member and said means to a value less thanthat effective to operate said first switch, an electric circuitincluding both of said switches, and means in said circuit actuated byconcurrent operation of said switches.

8. In a vacuum cleaner, a housing having an inlet opening, means forproducing flow of air into said housing through said in1et,'dustseparating members in said housing in the path of air flow between saidinlet in said means, a first element movable in response to variationsin air pressure ahead of said member, afirst electric switch closable bymovement of said first element resulting from an increase in pressure, asecond element movable in response to variations in air pressure betweensaid member and said means, a second electric switch closable bymovement of said second element resulting from a decrease in pressure toa value less than that effective to close said first switch, an electriccircuit including both of said switches in series, a magnetic device insaid circuit energized by concurrent closing of said switches, and athird switch operable by energization of said magnetic device forinterrupting the supply of current to said circuit. I

9. In a vacuum cleaner, a housing having an inlet opening, means forproducing flow of air into said housing throughsaid inlet, a dustseparating member-in said housing in the path of air flow between saidinlet and said means, a closure on saidhousing providing access to saiddust bag, latch means maintaining said closure in a closed position, afirst element movable in response to variations in air pressure ahead ofsaid member, a first electric switch closable by movement of said firstelement resulting from an increase in pressure, a second element movablein response to variations in air Pressure between said member and saidmeans, a second electric switch closable by movement-of said secondelement resulting from a decrease in pressure to a value less than thateffective to close said first switch, an electric circuit including bothof said switches in series, a magnetic device in said circuit energizedby concurrent closing of said switches, a third switch operable byenergization of said magnetic device for interrupting the supply ofcurrent to said circuit, and another magnetic device in said circuitenergized by concurrent closing of said switches and operable forreleasing said latch means. 7

10. In a vacuum cleaner, a housing having an inlet opening, means forproducing flow of air into said housing through said inlet, a dustseparating member in said housing in the path of air flow between saidinlet and said means, a first element movable in response to variationsin air pressure ahead of said member, a first electric switch operableby said first element and normally closed when said first element issubject to atmospheric pressure, said first switch being opened whensaid first element is subjected to certain sub-atmospheric pressures,said first switch thereby being closable by further movement of saidfirst element resulting from an increase in pressure above saidsub-atmospheric pressures, a second element movable in response tovariations in air pressure between said member and said means, a secondelectric switch operable by said second element and normally open atatmospheric pressure, said second switch being closable by movement ofsaid element resulting from a decrease in pressure to a pressuresubstantially below atmospheric pressure, an electric circuit includingboth of said switches in series, and means in said circuit actuated byconcurrent closing of said switches, whereby said circuit is actuatedonly inresponse to a predetermined sub-atmospheric pressure conditionoccurring concurrently ahead of said dust separating member and betweensaid dust separating member and said means for producing fiow of air.

11. In a vacuum cleaner, a housing having an inlet opening, a motor-fanunit for producing fiow of air into said housing through said inlet, adust separating member in said housing in the path of air flow betweensaid inlet and said motor-fan unit, a closure on said housing providingaccess to said dust bag, latch means maintaining said closure in aclosed position, a first element movable inresponse to variations in airpressure ahead of said member, a first electric switch closable bymovement of said first element resulting from an increase in pressure, asecond element movable in response to variations in air pressure betweensaid member and said motor-fan unit, a second electric switch closableby movement of said element resulting from a decrease inpressure to avalue less than that effective to close said first switch, an electriccontrol circuit including both of said switches in series, a magneticdevice in said circuit energized by concurrent closing of said switches,a third switch operable by energization of said magnetic device forinterrupting the supply of current to said motorfan unit and saidcontrol circuit, and another magnetic device in said circuit energizedby concurrent closing of said switches and operable for releasing saidlatch means.

12. In a vacuum cleaner, a housing having an inlet opening, means forproducing flow of air into said housing through said inlet, a dustseparating member in said housing in the path of air fiow between saidinlet and said means, a first element movable in response to variationsin air pressure ahead of said member, a first electric switch operableby said first element and normally closed when said first element issubject to atmospheric pressure, said first switch being opened whensaid first element is subjected to certain sub-atmospheric pressures,said first switch thereby being closable by further movement of saidfirst element resulting from an increase in pressure above saidsub-atmospheric pressures, a second element movable in response tovariations in air pressure between said member and said means, a secondelectric switch operable by said second element and normally open atatmospheric pressure, said second switch being closable by movement ofsaid second element resulting from a decrease in pressure to a pressuresubstantially below atmospheric pressure, and an electric circuitincluding a time delay switch and both of said switches in series, andmeans in said circuit actuated by concurrent closing of said switches.

13. In a vacuum cleaner, a housing having an inlet opening, means forproducing fiow of air 17 into said housing through said inlet, a dustseparating member in said housing inthe path of air flow between saidinlet and said means, an inlet conduit extending inwardly from saidinletopen ing and having its inner end extending into said dustseparating member, said conduit having a cross sectionsubstantially lessthan that of said dust-separating member, an electriccontrolcircuit,-and means responsiveto an increase in pres surein saidinlet tube at a point spaced fr'om'the inner end thereof and to aconcurrent decrease in pressure between said dust separating. member andsaid means for producingflow of air: for actuating said control circuit.f Q

14. In a vacuum cleaner, a housing havingan inlet opening, means forproducing flow of air into said housing through said inlet, a dustsepa-irating member in said housing in the path of air flow between said inletand said'means, an inlet conduit extending inwardly from said inletopening and having its inner endv extending into said dust separatingmember, said conduit having a cross section substantially less than thatof said dust separating member, a first tube communicating with saidinlet conduit at a point spaced from the inner end thereof, a secondtube communicating with said housing at a point between said dustseparating member and said means for producing flow of air, an electriccontrol circuit, and means responsive to an increase of pressure in saidfirst tube and a decrease of pressure in said second tube for actuatingsaid control circuit.

15. In a vacuum cleaner, a housing, a dust separating member in saidhousing, means for producing flow of air through said member, anelectric control circuit, means for supplying current to said circuit,an electric switch for interrupting said supply, means operable byenergization of said circuit for opening said switch, and electricswitching means responsive to an increase in pressure ahead of saidmember and to a concurrent decrease in pressure behind said member forenergizing said circuit.

16. In a vacuum cleaner, a housing, a dust separating member in saidhousing, a motor fan unit for producing flow of air through said member,an electric control circuit, means for supplying current to said motorand to said circuit, an electric switch for interrupting said supply,means operable by energization of said circuit for opening said switch,and electric switching means responsive to an increase in pressure aheadof said member and to a concurrent decrease in ressure behind saidmember for energizing said circuit.

17. In a vacuum cleaner, a housing having an opening, a dust separatingmember removable from said casing through said opening, a closure forsaid opening, means for producing flow of air through said member, anelectric control circuit, means for supplying current to said circuit,an electric switch for interrupting said supply, means operable byenergization of said circuit for opening said closure and for openingsaid switch, and electric switching means responsive to an increase inpressure ahead of said member and to a concurrent decrease in pressurebehind said member for energizing said circuit.

18. In a vacuum cleaner, a housing having an opening, a dust separatingmember removable from said casing through said opening, a closure forsaid opening, a motor fan unit for producing now of air through saidmember, a manually operable switch for turning on and ofi the supply ofcurrent to said motonan electric control circuit connectedto be suppliedwith current through said switch, means operable by energi'z'ae tion, ofsaid circuit for opening saidclosurea'r'id f for opening said switch,and electric'switching meansresponsive to an increase in pressure aheadofsaid member and to a concurrent decrease in pressure behind saidmember for energizing said circuit.

19 In a vacuum'cleaner, a, housing having. inlet opening, means forproducing flow oi air into-said housing through said inlet, a dustseparating member in said housing in the path of air flow between saidinlet and said means, an

- inlet conduit. extending inwardly from .said .in-

let opening and having its inner end extending. into saiddust-separating member, said conduit. having a cross sectionsubstantially less-than current decrease in pressure between said dustseparating member and said means for producing flow of air for actuatingsaid control means.

.20. In a vacuum cleaner, a housing having an air inlet, a fan havingits suction connected to said housing for producing a flow of airtherethrough from said inlet, a dust separating member in said housingin the path of flow of air through said housing, said air inletcomprising a conduit communicating with the interior of said dustseparating member and having a crosssectional area substantially lessthan that of said dust separating member, a control means, and

fluid pressure means operatively associated with said control means,said fluid pressure means including a fluid passage connection to thespace between said suction fan and dust separating member and a fluidpassage connection into said conduit respectively and responsive duringthe operation of said fan to a decrease in pressure between said fan anddust separating member and to a concurrent increase in pressure in saidconduit to actuate said control means.

21. In a vacuum cleaner, a housing having an air inlet, a fan having itssuction connected to said housing for producing a flow of airtherethrough from said inlet, a dust separating member in said housingin the path of flow of air from said inlet through said housing, ahinged member for said housing pnoviding access to said dust separatingmember, releasable latch means for maintaining said hinged member inclosed position, control means for releasing said latch means, said airinlet comprising a conduit communicating with the interior of said dustseparating member and having a cross section substantially less thanthat of said dust separating member, and fluid pressure meansoperatively associated with said control means, said fluid pressuremeans including a fluid passage connection to the space between saidsuction fan and dust separating member and a fluid passage connectioninto said conduit and responsive during the operation of said fan to adecrease in pressure between said fan and dust separating member and toa concurrent increase in pressure in said conduit to actuate saidcontrol means for releasing said latch means.

22. In a vacuum cleaner, a housing having an air inlet, a fan having itssuctionconnected to said housing for producing a flow of airtherethrough from said inlet, an electric motor for operating said fan,a dust separating member insaid housing in the path of flow of airthrough said housing, an electric switch operable to interrupt supply ofcurrent to'said motor, control means for operating said switch, said airinlet comprising a conduit communicating with the interior of said dustseparating member and havinga cross section substantially less than thatof said dust separating member, and fluid pressure means including fluidpassage connections'to the space between said suction fan and dustseparating member and to the interior of said conduit respectively andresponsive during the operation of said fan to a decrease'in pressurebetween said fan and dust separating member and to a concurrent increasein pressure in said'conduit to actuate said control means to Operatesaid switch; 1

' V FERMAN- C. DOUGHMAN.

REFERENCES CITED The following references are of record in the fileoftlcis patent Orthe original patent:

. Number UNITED STATES PATENTS Name Date Davis Oct. 4, 1932 Smellie Apr.18, 1933 Lofgren Feb. 19, 1935 Martinet June 4, 1940 Hein Jan. 28,- 1941Helm-Hansen Mar. 2, 1943 Leathers June 1,1943 Baird Mfi,1'. '7, 1944Sparrow ..-'June 6,1944 McCleery Nov. 14, 1944 Goldsborough Oct. 9, 1945Bartholy Jan. 15, 1946 Wald May 7 1946 Kilto Oct. 29, 1946 Smellie Dec.31,1946

FOREIGN PATENTS Country Date Number Germany Oct. 23, 1937

